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THS: EFFECTS OF EXTENDED BED REST ON 
HUMAN SLEEP PATTERNS 



BY 

SCOTT S. CAMPBELL. 



A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY 
OF FLORIDA IN PARTIAL FULFILLMENT OF THE 
REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY 



UNIVERSITY OF FLORIDA 
1981 



Copyright 1981 

by 

Scott S. Campbell 



ACKNOWLEDGEMENTS 

The author v^fould like to thank the members of his supervisory 
committee for their assistance and criticism during the preparation 
of this dissertation. The author would especially like to express 
his deep appreciation to Dr. Wilse B. Webb whose encouragement, 
guidance, time, and patience provided a constant source of motivation 
and inspiration. Thanks likewise go to Brings, Lewis., Alton, and 
Gregg whose technical assistance and friendship were invaluable. 
And final thanks to my parents for their support, both moral and 
financial, without which the completion of this dissertation would 
have been impossible. 



m 



TABLE OF CONTENTS 

CHAPTER . PAGE 

ACKNOWLEDGEMENTS iii 

ABSTRACT vii 

ONE INTRODUCTION 1 

Sleep as a Biological Rhythm ........ 1 

Uniphasic or Ultradian ? 4 

TWO MEIHODS 12 

THREE RESULTS 15 

Initial Sleep Period .... 15 

Bedrest Period 17 

Circadian Considerations 24 



FOUR DISCUSSION 3 



v^O 



Total Sleep Time . 35 

Uniphasic or Ultradian? 49 

APPENDIX 

SLEEP QUESTIONNAIRE 53 

REFERENCES ........ . 55 

BIOGRAPHICAL SKETCH 60 



IV 



LIST OF TABLES 



TABLE PAGE 

I I Comparisons of sleep stage characteristics for 16 

baseline (Night 2), bedrest period, and norma- 
tive group. 

II Individual and group statistics for the bedrest 20 
period (BP) 

III Distribution of bedrest sleep periods by the 21 
presence or absence of REM and Stage 4 sleep. 

IV Comparison of sleep variables as a function of 25 
night (11 PM - 7 AM) and day (7 AM - 11 PM). 

V Sleep onset times of longest sleep episodes for 28 
Night 2 (baseline), 3, and 4. 

VI Comparison of sleep variables betv/een first and 31 
second 24 hours of bedrest period. 



LIST OF FIGURES 
FIGURE PAGE 

1 Placement of sleep/waking episode across 60 "IS 
hours for individuals and group. 

2 Example of sleep across BP (#932). 19 

3 Total number of subjects asleep, for each hour 26 
across the bedrest period. 

4. Proportions of TST spent in REM sleep, as a 29 
function of time of day. 



VI 



Abstract of Dissertation Presented to the Graduate Council 
of the University of Florida in Partial Fulfillment of the 
Requirements for the Degree of Doctor of Philosophy 



THE EFFECTS OF EXTENDED BED REST ON 
HUMAN SLEEP PATTERNS 

By 

Scott S. Campbell 

August 1981 

Chairman: Wilse B. Webb 

Major Department: Department of Psychology 

That the sleep response is one of numerous physiological functions 
v>'hich may be classified as a biological rhythm is well-established. 
Less well-founded, despite its popularity, is the notion that the 
sleep of adult humans maintains an inherent tendency to occur mono- 
phasically within each 24 hours, typically during the nocturnal por- 
tion of the 24-hour day. 

This dissertation addresses the hypothesis that self-imposed and/ 
or sociophysically mediated behavioral controls have a significant 
influence on the manifestation of such a uniphasic sleep patterr., 
and that attenuation of behavioral controls may result in a "loosening" 
of the drcadian framework of typical adult sleep. 

Each of 9 young adults was electrographical ly recorded over a 
period of 60 hours, during which behavior was restricted primarily to 
lying quitely in bed; i.e., subjects were not permitted to read, write, 

vi1 



listen to music > watch TV, exercise., etc. Meals v/ere served at random 
intervals, and subjects had no knowledge of time of day throughout the 
bedrest period (BP). 

The data indicate that a reduction in behavioral controls, which 
typically influence the sleep process, results in substantial altera- 
tions in the placement and periodicity of sleep. Sleep episodes became 
evenly dispersed across the 24-hour day, resulting in an approximate 6 
hour sleep/vvaking cycle. 

While the average sleep period duration decreased, mean total 
sleep time for the bedrest period (28 h) exceeded, by more than 40/iJ, 
that which vfould be expected under the assumption of a uniphasic sleep/ 
waking rhythm. The continued tendency toward a nocturnal weighting of 
total sleep v/as clear, however, since 55% of TST for BP occurred during 
the night (11PM to 7AM). 

Within sleep structure (e.g., sleep stage percentages, mode of 
appearance) was affected only slightly by the "loosening'' of the sleep 
response. REM sleep retained its tendency to occur differentially 
across the 24-hour day; stage 4 sleep appeared to maintain its rela- 
tionship to prior -wakefulness. 

It is suggested that the sleep/waking patterns observed in this 
study may he further manifestations of an inborn (albeit, highly, 
dampened) ultradian sleep/waking rhythm. 



vm 



CHAPTER ONE 
INTRODUCTION 



Slee p as a Biolo gical R hythm. That the sleep response is one of 
a vast array of physiological functions which maintain a reliable 
tendency to repeat at regular intervals has been demonstrated on 
numerous occasions over the past two decades (see for example, 
Aschoff, 1965; Richter, 1965; Symposia on Quantitative Biology, 
1960; Webb, 1971; Webb and Agnew, 1974a). That the modulation of 
the sleep/waking cycle is controlled by innate and autonomous 
mechanisms seems > also, to have been well established. 

In a free-running (time free) environment, subjects display the 
continuation of a sleep/waking rhythm which deviates slightly from 
the standard 24 hours (usually longer). The only plausible explana- 
tion for such a finding, according to Aschoff (1965, p. 1427) is 
"that this rhythm is not imposed on the organism by the environment, 
but is truly endogenous. We are dealing with a self-sustaining 
oscillation which is free-running under constant conditions and has 
its own inherent frequency." 

The autonomous nature of the sleep/waking rhythm may also be 
demonstrated in the free-running environment, relative to other 
rhythms. The vast majority of rhythms which are in phase with the 
sleep/waking cycle in the 24-hour environment become desynchronized 
upon introduction into the time free environment (Aschoff, 1978; 
Aschoff and Wever, 1976; Wever, 1973). An example of such 

1 



desynchronization is that which occurs between the temperature and 
sleep/waking rhythms. When both rhythms are entrained to 24 hours , 
the maximum temperature typically occurs just prior to retiring, and 
the minimum temperature occurs toward the end of the sleep period. 
However^ under free-running conditions, maxima and minima of rectal 
temperatures become independent of sleep onset and termination. 

In addition, the sleep/waking rhythm may be entrained to arti- 
ficial light/dark regimens while typically in~phase rhythms maintain 
their free-running periodicities. For example, throughout 10 days 
of entrainment to a 3 hour sleep/waking cycle, subjects' temperatures 
continued to exhibit characteristic circadian periodicities (Weitzman, 
Nogeire, Ferlow, Fukushima, Sassin, McGregor, Gallagher, and 
Hellman, 1974). Such data "contradict any hypothesis of a simple 
'cause-and- effect' relationship between the activity-- rest cycle and 
the rhythm of body temperature, and suggest a system of tv.'o coupled 
oscillations . . . with a mutual phase relationship which depends on 
the conditions" (Aschoff, 1978; p. 740). 

Further evidence of the sleep/waking cycle's autonomy relative 
to other biological rhythms may be seen in the results of sleep 
deprivation studies. In the absence of sleep (for more than 70 hours) 
measures of performance, temperature and endocrine function all 
showed continuation of endogenous ci radian rhythms (Murry, Williams, 
and Lubin, 1958; Froberg, Karlsson, Levi, and Lidberg, 1975, as 
cited by Aschoff, 1978). 

Examinations of the miaturation of the human sleep/waking rhythm 
have also provided evidence for its innate and autonomous natuv^e. 



After observing the development of an initial 25-hour periodicity in 
an infant maintained on a self-demand sleep- wakefulness and feeding 
schedule, Kleitman and Engelmann (1953) concluded that "there may be 
a 'natural' rhythm which only has to be adjusted to the 24 hour 
alternation of night and day" (p. 280). Other researchers have also 
observed the development of adult-like, primarily monophasic, 
nocturnally placed sleep under similar conditions of self-demand 
feeding (Parmelee, Wenner, and Schulz, 1964; Salzarulo, Fagioli, 
Salomon, Ricour, Raimbault, Amibrosi, Cicchi, Duhamel , and Rigoard, 
1980). 

While the sleep/waking rhythm clearly appears to be inborn and 
independently regulated, it may^ at the sam.e time be entrained by 
exogenous Zeitgebers, to frequencies other than those characteristic 
of the free- running environment. It has been demonstrated that 
human subjects are capable of maintaining sleep/waking cycles of 
various lengths, quite efficiently within a range of about 20 to 27 
hours, as the result of entrainment to appropriate light/dark regimens. 
It has been further shown that the sleep/vraking rhythm characteristic 
of a free-running environment may be regulated by "rigid control of 
the sleep portion of the cycle . . . particularly of the wakeup time" 
(Webb and Agnew, 1974b; p. 701). 

Several investigators also point to the developmental literature 
as a source of evidence for the entrainability of the sleep/waking 
rhythm (Ellingson, 1975; Gesell and Armatruda, 1945; Kleitman, 1963; 
Sander, Stechler, Burns, and Julia, 1970; Sterman, 1979). As 
expressed by Sterman (p. 213), "the development of sleep is a postnatal 



phenomenon, subject both to the dictates of physiological maturation 
and the influences of environment. Such factors as geography and 
social custom entrain the physiological substrates of the sleep-waking 
cycle to determine the behavioral patterns which will come to 
characterize these states in a given culture." 

Indeed, the \'ery fact that adult humans maintain a 24- hour 
sleep/waking periodicity, in spite of an inherent rhythm with a 
frequency longer than 24 hours, is clear evidence of the entrain- 
ability of the rhythm. 

It appears then, that the oscillation between sleep and vjake- 
fulness, characteristic of adult humian subjects, meets the criteria 
necessary for its designation as a biological rhythm. Sleep is an 
inborn, independently regulated, exogenously entrainable, regularly 
occurring response. 

Unipha sic or Ultradian? While sleep and wakefulness clearly 
comprise a physiological system which may be classified as a bio- 
logical rhythm, determination of the rhythm's inherent periodicity 
remains less clear, since few studies have been conducted which 
adequately address this point. It is generally assum,ed that the 
sleep/waking cycle is an uniphasic one. In addition to the obvious 
support for such a notion, i.e., that adult humans typically obtain 
sleep in a single, nocturnal block, results from studies in which the 
normal sleep period has been dispersed or eliminated have also been 
cited as evidence for this view. In such experiments, performance 
measures are usually lowest and subjective reports of sleepiness are 



usually greatest during the interval in which the subject v/ould 
normally be sleepinq (Colquhoun, 1971; Weitzman et al . , 1974). 

It has further been reported (Weitziiian et al . , 1974) that "a 
striking persistence of a circadian pattern of total sleep time" 
(p. 1020) was exhibited throughout 10 days of entrainment to a 3-hour 
day. In this study, subjects were encouraged to sleep 1 hour out of 
each 3 hours. The authors reported that the 4 sleep periods beginning 
at 3 AM, 6 AM,. 9 AM, and noon. accounted for 70% of the total sleep 
time. 

The decreased sleep efficiency associated with dispersed and 
displaced sleep schedules has also been seen as lending support to 
the notion of an inborn, nocturnal ly placed, uni phasic system of 
sleep and wakefulness. Studies in which the normal, nocturnal sleep 
period has been shifted to a time typically employed for work or other 
waking activities, indicate that such sleep episodes are characterized 
by significantly greater proportions of wakefulness (stage 0) after 
initial sleep onsets as compared to baseline (normal) sleep (Webb, 
Agnew, and Williams, 1971). Such findings suggest that the main- 
tenance of sleep is more difficult when the sleep period is shifted 
from its typical, nocturnal placement. Further, as experim.entally . 
circumscribed 'days' deviate from the normal 24 hours, sleep 
efficiency (amount of time in bed spent asleep), becomes less. 
Webb and Agnew (1975) found that subjects maintaining a sleep/waking 
schedule of 3 hours sleep/6 hours wakefulness only achieved 80% 
sleep efficiency wlien compared to baseline conditions (8 hours sleep/ 
16 hours wakefulness). Weitzman et al . (1974) reported 56% sleep 



efficiency for subjects attempting a 3-hour cycle compared with 90% 
efficiency for the baseline condition. 

It has also been noted in dispersed, as well as displaced sleep, 
that the intrasleep structure of the "new" episodes differs in several 
details from that seen in normally occurring nocturnal sleep. For 
example, Weitzman et al . (1974) observed "early" REM periods (preceded 
by less than 10 minutes stage 2 at sleep onset) and "sleep onset" REM 
periods (py^eceded only by wakefulness or stage 1) in over half of all 
REM episodes recorded over the 10 days of 3-hour sleep/wake scheduling. 
Results of the displacement of subjects' typically nocturnal sleep into 
day sleep include significant increases in the amiount of stage 1 and 
reductions in the amounts of stages 3 and 4 (Webb and Agnew, 1978). 
Such findings lend further support to the view that these sleep epi- 
sodes differ substantially from endogenously modulated sleep periods. 

It may be argued, however, that studies of sleep dispersion and 
and displacement do not adequately address the question of the in- 
hei^ent frequency of the sleep/waking cycle. Rather, such studies 
more specifically test the entrainability of the presumed uni phasic 
rhythm. Failure to effectively impose a shortened regimen upon a 
hypothesized uniphasic rhythm does not necessarily rule out the exis- 
tence of an ultradian sleep/waking rhythm. Yet, data supporting such 
a possibility are not extensive. 

One type of evidence used to support the suggestion that the 
human sleep/waking rhythm is inherently ultradian is provided by the 
analysis of sleep patterns of individuals participating in Polar 
expeditions. Lewis (1961; Lewis and Masterton, 1957) has suggested 



that given a situation in which adherence to customary circadian 
scheduling is less stringently controlled, a more accurate reflection 
of the inborn sleep/waking rhythm may emerge. 

In the Polar regions the photoperiod is not diurnal, but seasonal. 
Further J expeditions into these regions typically maintain little 
resemblance to an organized community, in that there are few circum- 
scribed daily routines, no specific feeding schedules, few timetables 
(Lewis, 1961). Sleep records from 5 Polar campaigns suggest that the 
organization of sleep/waking patterns was a direct function of the 
stringency with which the "community" was structured. For example, 
members of the British North Greenland Expedition (1952-54) were 
allowed to sleep as long as they liked, at virtually any time they had 
the inclination to do so. Under such conditions, sleep durations per 
24 hours did not increase substantially over baseline amounts. Yet, 
the length and placement of individual sleep episodes showed con- 
siderable deviations from members' normal sleep habits recorded in 
England. The tendency tov/ard polyphasic sleep placement was most 
extreme during the three months of continuous light or darkness. 
"During these periods . . . men used any of the 24 clock-hours for 
sleep. The winter months were characterized by many interruptions to 
sleep and by the taking of naps" (Lewis, 1961, p. 325). Although 
no data were presented relative to the rhythmicity of these multiple 
sleep episodes, it appears that the uniphasic "nature" of the sleep 
process loosened somewhat under conditions of limited environmental 
cues and negligible behavioral and cultural restraints. 



Within the more structured hours of daily life, it has been 
suggested that the ultradian nature of sleep and wakefulness may be 
manifest in the form of naps (Webb, 1978). Webb's proposal that naps 
are part of an inborn sleep/waking rhythm is based on the contention 
that certain characteristics of these intemrittant sleep episodes 
match features which are common to biological rhythms in general. 
Specifically, it is maintained that naps are: 1) temporally repeti- 
tive, 2) species specific, 3) often developmental, 4) innate and 
unlearned, 5) endogenous, and 5) adaptive. While evidence seems to 
support the first four characteristics, and only post hoc specula- 
tion can address the sixth, Webb points out that experimental 
support for the claim that naps are endogenously mediated is 
extremely limited, and that further data are "likely to be slow 
forthcoming." This is due primarily to the fact that virtually 
all procedures utilized for the examination of presumed biological 
rhythms have prohibited other-than-circumscribed sleep episodes 
as a consequence of experim.ental design considerations. Such experi- 
ments typically focus on the interactions of major components of 
sleep, waking and perfot^mance. As such, "the very nature of naps 
in these designs are uncontrolled and interfering sources of experi- 
mental variance" (Webb, 1978 p. 316). Two primary designs of this 
type are the free-running and bedrest procedures. 

It has been noted that the sleep/waking rhythms maintained by 
subjects in free-running environments provide excellent support for 
the notion that such rhythms are innately and independently controll- 
ed. Under such conditions, time cues are removed from the 



environment, but other behavioral controls are typically left 
unaltered. That is, subjects are asked to lead a "normal" life, 
including eating three meals a day in normal sequence, having the 
opportunity for exercise and other activities such as reading, 
writing, watching TV, etc., and maintaining circumscribed sleep 
schedules (no naps). As a result, these subjects have a tendency 
to carry on day-to-day life in a manner to which they have grown 
accustomed over the years. Clearly, such circumstances may strongly 
bias behavior toward a circadian schedule, perhaps entraining an 
inherently ultradian rhythm to an environmentally and culturally 
modulated circadian framework. These factors notwithstanding, 
the sleep patterns displayed by subjects in time free environments 
have been seen as providing evidence not only for the biological 
basis of the sleep/waking rhythm, but for its circadian (uni phasic) 
nature, as well . 

The latter inference seems tenuous, at best. For, when controls 
on the number and placement of sleep episodes are reduced in free- 
running environments, evidence seems to indicate that the "normal 
sleep pattern" (single sleep period of from 7 to 10 hours with 
occasional napping) is modified. Webb and Agnew (1974a) reported 
that under such circumstances "a significant increase in both long 
and short periods of sleep, compared to the 24-hour environment" (p. 
620) resulted. While neither the placement nor the periodicity of 
the increased episodes was analyzed, the authors concluded that such 
changes in the sleep response showed the extent to which the 
uni phasic sleep pattern is disrupted by reduced controls on sleep 
placement. 



10 

While studies employing a bedrest design may clearly eliminate 
some behavioral controls left in tact by the free-running design 
(most notably physical exercise), this procedure is also typically 
characterized by experimentally circumscribed sleep periods as a 
consequence of full schedules of psychological, psychophysiological 
and performance testing (see for examples Ryback & Lewis, 1971; 
Ryback, Lewis & Lessard, 1971), 

One recently published study (Nakagawa., 1980) however, does 
py^ovide some insight into sleep/waking cycles in the absence of 
cultural mediation and behavioral controls. In this study, subjects 
were required to remain lying quietly in bed for 10 to 12 hours 
immediately following a full night's sleep. The original aim of 
the study was to "elucidate changes in daytime states of conscious- 
ness" by observing "the LEG patteiTis of (awake) subjects in restrained 
postures under minimally changing experimental conditions" (p. 524). 
Despite explicit instructions to remain awake during the 10 to 12 
hour period, however, subjects experienced "an uncontrollable 
desire to fall asleep," resulting in sleep/waking cycles of approxi- 
mately 4 hours across the experimental period. Again, it appears 
that the uniphasic placement of the sleep process loosened in response 
to a reduction in behavioral controls. 

In summary, most designs employed in the investigations of 
the human sleep/waking rhythm are inadequate for that purpose since 
they include strict controls over waking and sleeping as a necessary 
part of the procedure. However, results from studies in which 
such controls are relaxed indicate that subjects have a tendency to 



11 



relinquish their typical uniphasic sleep placement in favor of a 
more dispersed^ polyphasic sleep system. 

The present study attempted to address the hypothesis that 
behavioral, cultural and environmental factors serve to entrain an 
inherently ultradian sleep/waking rhythm to a uniphasic, 24-hour 
framework by imposing upon the organism a series of behavioral 
controls. In tiie experimental environment, such controls are 
frequently mimicked by circumscribed sleep/v/aking schedules, feeding 
regimens and testing procedures. These external controls "may create 
incompatible responses which suppress the expression of (the) 
rhythmic response or create such a 'noise' background as to not 
permit measureiiient" of the hypothesized ultradian rhythm (Webb, 1978 
p. 315). Therefore, by minimizing "incompatible responses" and "noise 
background" the present study sought to "emancipate" the hypothesized 
ultradian rhythm from control by a self-imposed and/or sociophysical- 
ly mediated circadian framework. By so doing, it was proposed that 
the presence of such a rhythm may be more readily observed and 
measured. Specifically, subjects were required to maintain relative- 
ly static, basal levels of behavior over a period of almost three 
days, during which time their sleep/waking behavior was the primary 
variable of interest. 



•••.•-•il_-.;««'-^ .f"^ 



CHAPTER TWO 
METHODS 



The subjects for this study vrero 10 young adults (5 males and 
5 females) ranging in age from 18 to 25 years (mean =^ 20.4). Sub- 
jects were selected after questionnaire (Appendix 1) responses 
revealed normal sleep patterns and the absence of chronic health 
problems and/or acute illness. 

Each subject slept for 2 nights in the laboratory immediately 
prior to the beginning of 60 consecutive hours of bedrest. Between 
the 2 nights in the laboratory subjects were permitted to maintain 
their normal daily schedules with the stipulation that no naps be 
taken and no drugs (including alcohol and caffeine) be ingested 
during that period. 

For each session, 2 subjects reported to the laboratory approxi- 
mately Vi hours prior to their normal bedtimes (about 11 PM) for 
electrode placement. Five millimeter gold disc electordes were 
applied over Cambridge electrode jelly and held in place by collqdian 
saturated gauze strips. EEG and electrooculogram (EOG) were contin- 
uously monitored for each subject using a Grass Model VI electro- 
physiograph. The EEG of each subject was recorded on three channels 
between electrode sites Fpl - F7, PI - T5, and C3 - A2. The EOG 
was monitored on a separate channel by electrodes placed on the 
external canthus of each eye. 

12 



- J'Tj-^^V- -•»— — 



13 

At the completion of electrode placement each subject retired 
to a private, electrically shielded^ sound attenuated, temperature 
controlled room. Each subject's record was scored in one-minute 
epochs, following the methods described by Agnew and Webb (1972a). 
Cross-scoring of random 2-3 hour segments of the sleep portions of 
each record revealed a between-scorer reliability of greater than 
90%. 

Sleep onset was determined by the appearance of the first 
spindle or K-complex (Agnew & Webb, 1972b). A sleep period was 
considered as such v^^hen sleep continued, uninterrupted by more than 
20 minutes of wakefulness, for at least 30 minutes. A waking period 
was defined as Stage EEC for at least 20 minutes. 

Timing of the 60 hours of bedrest began with the spontaneous 
awakening of each subject from his/her second night of laboratory 
sleep and the subject's verbal report that he or she felt rested 
and had had enough sleep. At this time subjects were given an op- 
portunity to eat breakfast and use the bathroom. No intentional 
time cues were given the subjects upon awakening nor at any other 
time throughout the bedrest period, with the exception that each 
subject was told when he or she was "past the halfway point" at a 
random time after 30 hours had past. However, uncontrollable, gen- 
eral time cues from exogenous sources (eg., nearby building construc- 
tion, general building noise during working hours, homecoming fes- 
tivities during one session (subjects 945 & 946)) were present in 
varying degrees from session to session. 

During the 60 hours of bedrest, subjects were allowed minimal 
exogenous stimulation. Activities such as reading, writing, listening 



14 



to music or watching television vere prohibited. Conversations' 
during the period were limited to brief dialogues with the experi- 
menter at meal times. No instructions were given relative to when 
or when not to sleep. Subjects were asked to lie as quietly as pos- 
sible, but were permitted to change positions in bed when inclined 
to do so. Closed circuit TV monitors were employed to insure adher- 
ence to the experimental instructions. Subjects were permitted to 
go to the bathroom (in room) at their convenience and were allowed 
to sit up in bed during meals. 

Meals were served unsystematically (alwtiys during an ongoing 
waking period, as determined by the EEG) and consisted of a choice 
of several types of sandwiches, vegetable dishes, desserts and non~ 
caffeinated beverages. A maximum of k hour was permitted for the 
completion of each meal. Several types of fruit and a pitcher of 
ice water were also available to each subject ad libitum. 

Illumination in each room was provided by a 60 watt lamp placed 
on a table by the subject's bed, and control of light and control of 
light and darkness was at the discretion of each subject. 



CHAPTER THREE 
RESULTS 

One of" the '10 subjects terminated participation prior to the 
end of the bedrest period. Since only 12 hours of bedrest were re- 
corded for this subject, the results presented here are those of the 
9 subjects who completed the session. 

The criterion used here to define a "sleep period" (i.e., 30 
minutes of sleep, uninterrupted by more than 20 minutes of wakeful- 
ness) accounted for 91.3% of all sleep recorded. Eight sleep episodes 
had durations of less than 30 minutes (mean = 7.25 min., range = 2 
to 18 min.), and therefore v/ere not considered "sleep periods" in the 
following analyses. 

Initial Sleep Period . The mean total sleep time (TST) for the 
sleep period immediately preceding the onset of the bedrest period 
(Night 2) was 8.72 hours, with a range of from 5.82 hours to 10.43 
hours. Sleep stage peixentages for the period vrere generally within 
normal limits. However, as shown in Table 1, there was a significant- 
ly greater proportion of Stage 0, t (df = 39) - 2.32, p.<05 (all 
levels of significance are based on a two-tailed test), and a 
smaller percentage of stage 1, t(39) = 5.04, p.<001, and stage 3, 
t(39) = 2.20, p.<05, in this sample as compared with a normative 
group of 16 males and 16 females of approximately the same age (mean = 
24 years) previously recorded in the same laboratory (Williams, Agnew 
and Webb, 1964; 1966). "Chopping" each record to an artifical maximum 

15 



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17 



of 8 hours for Night 2 (i.e., scoring no. more than the first 460 
minutes of each record) did not significantly change the mean pro- 
portions of sleep stages as compared to 'intact' Night 2, but such a 
procedure did reduce the proportions of stages and 3 so that they 
were not significantly different relative to the normative group. 

Bedrest Peri od . Although timing of the bedrest period (BP) be- 
gan with the spontaneous awakening from Night 2 and the subject's 
acknowledgement that (s)he felt awake and rested, later analysis of 
the records of tliree subjects indicated that the 'spontaneous awaken- 
ings* were less than 20 minutes in length (7, 9, and 11 minutes) and 
were followed by substantial sleep episodes (mean = 2.11 hours). These 
episodes, therefore, v/ere included in the initial sleep period (Night 
2), and as a result, the bedrest periods of the 3 subjects were some- 
what under 60 hours (mean - 55.32 hours). The mean duration of BP 
for the entire group was 58.8 hours (range = 53.1 to 62.2 hours)/ 

Referring to Table 1 it can be seen that the sleep stage per- 
centages averaged from sleep periods occurring during BP differed 
only slightly from those recorded during Night 2. There were non- 
significant increases in the proportions of stages 0, 1, and 2, while 
nonsignificant decreases in SWS and REM sleep were observed as com- 
pared to Night 2. Similar trends (all significant, however) were 
observed relative to the normative group, with the exception of 
stage 1, which comprised a smaller percentage of TST across BP than 
in the normative sample. 

The distribution of sleep and wakefulness across BP, for all 
nine subjects^ is presented in Figure 1, Figure 2 presents, in 



18 




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22 



detail, the sequencing of sleep and wakefulness of one subject (932) 
across the bedrest period. Individual and group statistics for the 
entire bedrest period are presented In Table II. BP was character- 
ized by an alternation of waking periods with an average length of . 
2.7 liours (range = .4 to 10.2 hours) and sleep periods with a mean 
duration of 2.99 hours (range - .5 to 11.6 hours). Subjects spent 
almost half of BP asleep (47.6%) with a mean total sleep time of 
28 hours (range = 20 to 37.3 hours). Sleep was dispersed across an 
average of 9.3 episodes during the bedrest period (range = 5 to 13). 

These results are in contrast to what would be expected under 
the assumption of a uni phasic model of sleep. Under such an assump- 
tion , one would predict 2 discrete sleep episodes across the 60 hours ; 
placed within the normal nocturnal periods (approximately 11 PM to 
7 AM) 5 with a mean TST for the bedrest period of about 16 hours 
(about 27% of BP). 

Sleep periods during BP could be divided Into four general 
categories based on the presence or absence of stage 4 and REM sleep, 
as shown in Table III. Seventy percent (59) of all sleep periods 
recorded over the bedrest period were 'full blown' sleep episodes, 
1n that all stages of sleep were observed. Of the remaining 25 
sleep periods, 3 (all day episodes) showed neither REM nor stage 4 
sleep. Nine sleep periods (8 days, 1 night) exhibited an absence of 
REM sleep and 13 (12 days, 1 night) showed no stage 4 sleep. 

The mean period length of those episodes with neither REM nor 
stage 4 was 61 minutes. The mean duration of 'noREM' sleep periods 
was 65 minutes, and the '■noStg4'- sleep episodes averaged 84 minutes 



23 



duration. This is compared to a mean duration of 225 minutes 
(3.75 h) for those sleep episodes v/hich contained both stage 4 and 
REM. 

The occurrence of these events in terms of sidereal time was 
also examined, The three periods containing no REM and no stage 4 
occurred after noon and before the onset of the night phase (11 PM). 
All but 2 of the 'noREM' periods occurred betv;'een 2 PM and 10 PM. 
The 'noStg4' episodes occurred across the entire day phase (7 AM to 
11 PM) with only one such episode occurring at 'night' (G:40 AM). 

Regarding the mode of appearance of REM sleep episodes, of 153 
REM periods recorded over BP, only 3 were characterized by onsets at 
the beginning of a sleep period. Sleep onset REM periods (SOREMPS) 
were defined as those REM episodes occurring at the onset of sleep 
which were not preceded by more than 1 minute of stage 2. Two sleep 
episodes containing SOREMPS also were characterized by the absence of 
stage 4 sleep. The SOREMPS were contributed by 3 subjects , had a 
mean duration of 15.3 minutes (9, 10^ and 27 minutes), and occurred 
at approximately 6:30 AM, 6:30 PM, and 1:30 PM, respectively. 

In an effort to further elucidate the factors involved in the 
cycling of REM sleep, two examinations were made. In the first pro- 
cedure, the REM sleep cycle (defined as the interval between the on- 
set of one REM period and the onset of the next) was calculated for 
each subject's baseline night (Night 2). The onset points of the 
cycle were then superimposed across each subject's entire bedrest 
period (including waking episodes) to test the hypothesis that the 
REM cycle was independent of prior sleep time. Alsp, the cycle was 



24 



superirnposGd across each subject's 'compressed' bedrest period, in 
which waking intervals were removed to obtain a continuous sleep per- 
iod, to test the possible sleep dependency of the REM sleep cycle. 
The initial onset of the superimposed cycle corresponded to the onset 
of the last REM sleep period of Might 2. 

The relationship between the superimposed REM cycle and the oc- 
cun^ence of actual REM episodes was examined by calculating tiie mean 
difference between each onset point of the hypothesized cycle and th;; 
closest REM epoch within that sleep period. The average difference 
between each onset of the superimposed cycle and the appearance of an 
actual REM epochs across the intact bedrest period, was 15.8 minutes 
(SD = 3.7 min). The mean difference between the values for the 'com- 
pressed' BP was 14.5 minutes (SD =4.7 min). The difference between 
the two conditions v/as not significant. 

To further test the sleep dependency of the cycle, the mean REM 
cycle length of the 'compressed' BP, for the group, was determined. 
Again^ beginning the cycle with the onset of the last REM period of 
Night 2, mean cycle length for the 'compressed' BP was 96.84 minutes 
(SD -■= 10.42 min). This is compared with a mean REM cycle length of 
96.56 minutes (SD = 12.76 min) for Night 2. 

Circadian Con sidera t ions . There were considerable differences 
in several measures as a function of time of day. For comparative 
purposes, waking and sleep periods were considered daytime events 
if they were initiated between 7 AM and 11 PM. Nighttime events 
were defined as those episodes with onsets between 11 PM and 7 AM. 



25 



TABLE IV, - Comparison of sleep variables as a function of night 
(11 PM 7 AM) and day (7 AM ~ 11 PM). 



Overall Night Day 



Mean TST 27 ,.,99 h 15.34 h 12,65 h 

(5.39) (3.30) (4.91) 

Mean Sleep 2.99 h 5.52 h ** 1.93 h 

Period Length (2.35) (2.65) (.98) 

Total # Sleep 84 25 59 

Episodes 

Sleep/Wake 6.10 h 7.81 h * 5.25 h 

Cycle Length (2.68) (3.26) (1.74) 

% Stage 3.59 3.50 3.54 

(3.58) 

% Stage 1 3.28 3.88 2.81 

(2.06) 

% Stage 2 58.41 56.37 60.80 

(6.22) 



6.10 h 
(2.68) 


7.81 h 
(3.26) 


3.59 
(2.28) 


3.50 
(2.26) 


3.28 
(1.87) 


3.88 
(2.79) 


58.41 
(4.94) 


56.37 
(5.76) 


4.33 
("1-24) 


4.13 
(1.58) 


9.86 
(4.54) 


8.89 
(5.37) 


20.47 
(2.94) 


23.13 
(4.01) 


** p <.001 t test, 
* p < . 01 


two-tailed 



% stage 3 4.33 4.13 4.94 

(1.75) 

% stage 4 ' 9.86 8.89 11.01 

(4.28) 

% Stage REM 20.47 23.13 ** 17.54 

(3.87) 



Mean 
(SD) 



26 



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27 



Of 84 total sleep episodes v^ecorded for the group across the 
bedrest period, 59 (70.2%) occurred during the day and 25 (29.8%) 
occurred at night. Hov/ever, over half of the total sleep time (54.7%) 
during BP was obtained during episodes initiated between 11 PM and 7 
AM. 

Comparisons betK'een day sleep periods (DS) and night sleep 
periods (NS) of temporal measures and sleep stage percentages are 
shown in Table IV. The most notable difference in measures of DS and 
MS was with regard to mean sleep period duration. NS episodes con- 
tinued for a mean duration 5.52 hours (SD = 2.65 h) compared to an 
average length of 1.93 hours (SD = .98 h) for sleep episodes 
initiated during the day (t (82) = 6.58, p<.001). Conversely, the 
mean duration of waking episodes v/as 1.47 hours (SD = 1.04 h) for 
nighttime events and 3.12 hours (SD = 2.4 h) for those initiated 
during the day (t (82) = 4.29, p<.001). Consequently, the sleep/ 
waking cycle length (defined as the interval between the onset of 
one sleep episode and the onset of the next) increased significantly 
from day (5.25 h, SD - 1.74) to night (7^81 h, SD = 3.26) t (73) - 
2.89, p<.01. 

Figure 3 presents, by hours, the number of subjects sleeping_ 
across the bedrest period. The group tendency toward nocturnal 
sleep placement is evident. Of 144 total subject-hours available for 
sleep during the 2 night periods (11 PM to 7 AM), 104 (72.3%) were 
used for that purpose. In contrast, of the 279 subject hours com- 
prising the first and second day periods (8 AM to 11 PM and 7 AM to 
11 PM) less than half (45,2%), were spent sleeping. 



28 



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30 



The possible presence of a free-running sleep/wake rhythm was 
examined by comparing the mean sleep onset time of Night 2 (baseline) 
and the mean onset times of the lonv^est sleep periods of Nights 3 and 
4. The mean sleep onset times For the group exhibited a tendency to, 
occur later on each succeeding night--slightly under 1 hour later 
on Night 3 (as compared to baseline) and 42 minutes later on Might 
4 (as compared to Night 3), However, as shown in Table V only 2 
subjects (929 and 937) demonstrated consistent free-running patterns 
across the three nights. Four additional subjects delayed the onset 
of their major nocturnal sleep onset on Night 4 (relative to Night 3). 

Sleep stage percentages V\fere not affected substantially as 
a function of time of day. While there was slightly less stage 1 
(2.8 vs 3.9%) and slightly more stage 2 (60.8 vs 56,4%) and stage 4 
(H vs 8.9%) during the daytime sleep periods, only the difference 
in REM sleep percent v-;as significant, with F^EM sleep comprising just 
over 23% of NS episodes and only 17.5% of DS periods (t (82) = 5.91, 
p<.001). The difference in REM percent appeared to be a consequence 
not only of the difference in sleep period length but also of the main- 
tenance of a circadian pattern of REMS across the the bedrest period., 
as shown in Figure 4, The largest proportion of TST spent in REM 
sleep occurred during those sleep episodes initiated between 4 AM and 
8 AM, The proportion of REM sleep decreased across the "next three 4-- 
hour time blocks. until reaching a low of 11,57% of TST for sleep 
episodes initiated between 4 PM and 8 PM. The percentage of REM 
sleep then exhibited a steady increase across the subsequent 4-hour 
time blocks (8 PM to 12 MID and 12 M to 4 AM). 



31 



TABLE VI, - Comparison of sleep variables, between fi.rs.t ^ind second 24 
hours of bfidresit period. 





Overall 


1st 24 HRS 


2nd 24 MRS 


Mean TST 


27.99 h 
(5.39) 


14.46 h 
(2.28) 


<* 10.97 h 
(2.36) 


Mean Sleep 
Period Length 


2.99 h 
(2.35) 


3.54 
(1.92) 


2.82 h 
(1.44) 


Total # Sleep 
Episodes 


84 


39 


33 


Sleep/Wake 
Cycle Length 


6.10 h 
(2.68) 


5.19 h 
(2,10) 


5,64 h 
(2.04) 


% Stage 


3.59 . 
(2.28) 


2.94 
(2.23) 


4.48 
(4.25) 


% Stage 1 


3.28 
(1.87) 


3.03 
(1.93) 


3.74 
(2.66) 


% Stage 2 


58.41 
(4.94) 


59.69 
(4.03) 


56.68 
(8.50) 


% Stage 3 


4.33 
(.1.24) 


4.15 
(1.40) 


4.66 
(1.58) 


% Stage 4 


9.86 
(4.54) 


8.39 
"(3.60) 


11.39 
(6.88) 


% Stage REM 


20.47 
(2.94) 


21.77 
(2.56) 


19.02 
(4.82) 



Mean ** p < , 01 

(SD) t test, two-tailed 



In addition to day/night differences, there was also disparity 
in temporal measures as a function of elapsed time within the bedrest 
period. Table VI compares TST, sleep period duration, sleep/v/aking 
cycle length, and sleep stage percentages recorded during the first 
24 hours of bedrest with those recorded during the second 24 hours. 
Total sleep time for the first 24 hours (14.5 h) was significantly 
longer than TST for the second 24 hours (10.9 h) (,t (16) = 3.19, p< 
.01). While the decrease in TST was. in part attributable to a 
reduction in the total number of sleep episodes during the second 24 
hours (39 vs 33), a decline in the m.ean sleep period length across BP 
(3.54 h vs 2.82 h) also contributed to the difference. 

Despite the decrease in overall sleep period duration, the 
sleep/waking cycle length remained essentially uncfianged throughout 
the bedrest period. For purposes of comparison, only those sleep/ 
waking cycles initiated and completed within one or the other 24 hour 
periods v;ere considered. The mean duration of sleep/waking cycles 
occurring during the first 24 hours was 5.2 hours (SD = 2.1 h), while 
the mean cycle length of those completed during the second 24 hours 
was 5.6 hours (SD = 2.4 h). 

There were no significant differences in sleep stage proportions 
between the 24-hou'^ intervals. However, trends were observed relative 
to stages 4 and REM. Stage 4 increased (from 8.4 to 11 A%) from the 
first 24 hours to the next; this despite the fact that there were 
more sleep episodes containing stage 4 in the first 24 hours (32 vs 
27). Conversely, REM sleep decreased by over 10% from the first to 
the second 24 hours. 



CHAPTER FOUR 
DISCUSSION 



The results of this study substantiate and further detail pre- 
vious reports that a reduction in the control of the sleep response 
results in a 'loosening' of the uniphasic, nocturnally placed sleep 
pattern typically observed in adult humans. At the same time, hov/- 
ever, the results underscore the tendency of sleep to be differen- 
tially weiglited toward a definite and persistent nocturnal placeiiient. 

On the one hand, the data suggest a quadri phasic sleep patterns 
with the onset of sleep episodes occurring at approximately 5 hour 
intervals throughout the bedrest period. While such a rhythmicity 
proved to be highly variable within subjects, from one sleep period 
to the next, the relatively small between-subjects variability em- 
phasizes the regularity of such a rhythm within the group. That the 
number of sleep periods was proportionately placed, relative to day 
and night, further accentuates the uniform distribution of sleep epi- 
sodes across the 24-hour day. The 'day' phase (7 AM to 11 PM) com- 
prised approximately 73% of the total bedrest period. Corresponding! 



J' 5 



70X (59) of the total number of sleep episodes recorded- across BP were 
initiated during the day. 

On the other hand, comparison of the mean duration of those day 
sleep periods with the average length of sleep periods initiated at 
night clearly illustrates the substantial orientation toward the 

33 



34 

nocturnal placement of total sleep time. Over half (55?) of the total 
sleep time recorded during BP was obtained during sleep periods initi- 
ated between 11PM and 7AM, despite the fact that 'night' comprised only 
27% of the total bedrest period. 

These findings are in accord with those reported by Weitzman. et al 
(1974) relative to tfie placement of the sleep of subjects maintained on 
a 3-hour 'day'. In that study, the sleep of 7 subjects exhibited a 
strong tendency to occur during the scheduled sleep periods beginning 
at 3AM, 6AM, 9AM, and noon. While the authors note the shift away from 
typical sleep placement (i.e., 11PM - 7AM) du.ring the 10 days of ultra- 
dian cycling, they emphasize the "highly resistant nature" of the 
circadian loading of the sleep response. 

Webb and Agnew (1974a) also noted a tendency for subjects to 
maintain a circadian, primarily nocturnal, placem.ent of total sleep 
time in a free-running environment. The authors cite three aspects of 
their findings which suggest a continuation of "the entrained influence 
of the original 24-hour cycle." First, several subjects showed sleep 
onset times during the first 3 or 4 days which were significantly 
earlier than would be predicted by a pure free-running hypothesis. 
Secondly 5 throughout the 14 days of the study, there were tendencies 
on the parts of 5 of the 7 subjects for sleep onset times to 'regress' 
periodically, thereby increasing the probability that sleep onset 
would occur during the nocturnal phase (between midnight and 7AM). 
Finally, there were two occasions in which subjects skipped sleep 
periods, the predicted onsets of which would have occurred during the 
day phase (specifically, noon and 4PM), and instead delayed initiation- 
of the next sleep periods to nocturnal placements (IIPM and 3AM, 
respectively) . 



35 



The tendency toward a free-running sleep/waking cycle was not 
apparent in the present study. While the mean sleep onset times of 
the major nocturnal sleep episodes became successively later across 
the three nights, only 2 individuals exhibited such a tendency. Other 
subjects delayed sleep onset on Night 3, only to advance onset time on 
Night 4. Still others exhibited a reverse trend. Such 'scalloping' 
of the expected free-running rhythm in the present study may reflect the 
continued inclination of some subjects to maintain their sleep in its 
typical nocturnal placement. 

Total Sleep T ime. The results of the present study are also 
consistent with previous findings relative to the amount of total sleep 
obtained. In summing up the findings on studies of unrestricted sleep, 
Webb and Agnew (1975a) noted that "it may now be stated with ccnfi dance 
that permitting subjects to sleep ad lib under conditions which have 
not increased the sleep need by prior deprivation or increased energy 
expenditure will consistently result in increased sleep length," (p., 369). In 
addition, sleep logs maintained across several weeks reveal that average 
weekday ('restricted') sleep and weekend ('unrestricted') sleep differs 
by an hour or more (Johns, Gay, Goodyear, and Masterton, 1971; Webb, 
1981; White, 1975). 

The subjects in the present study were instructed; on Night 2, to 
sleep until they felt well-rested and no longer sleepy. The m^ean sleep 
duration for Nignt 2 (8.7 hrs) was within minutes of the mean total 
sleep time (8.8 hrs) reported for 4 subjects (10 nights each) per- 
mitted to sleep as long as they wished, following 10 nights of 
'restricted' sleep which averaged 7.4 hrs per night (Webb and Agnew, 



■. -.-n .*■-»*> 



35 

1974a). The mean sleep length for Night 2 is also in agreement with 
self-reported extensions in weekend sleep lengths (about 8.5 hrs). 

The mean total sleep time reported here is, however, almost an 
hour less than that of young adults (9.6 hrs) studied by Verdone (1968) 
and Webb and Agnew (1975a). It seems likely that the mean total sleep 
time for Night 2y like typically reported weekend sleep, was a conse- 
quence of the relaxation of self-imposed controls on sleep length 
(e.g., alarm clocks), rather than an expression of the complete satis- 
faction of sleep 'need'. Several subjects in the present study were 
rather impatient to terminate Night 2 and to initiate the bedrest 
period. This is illustrated by the case of one subject who reported, 
during a brief (3 min) av/akening, that she felt rested and had "had 
enough sleep." The report came after approximately 2 hours had elapsed 
in Night 2, Clearly, such eagerness to 'get on with it' may have 
resulted in the termination of sleep prior to the spontaneous ending of 
sleep due to satiety. 

A more accurate measure of maximum sleep length may be derived 
from the examinations across the bedrest period, of sleep durations per 
24 hours. Beginning with the termination of Night 2 (typically around 
SAM) the first .24-hour- period was characterized by an average of 14.5 
hours of sleep, the second 24 hours contained an average of almost 
11 hours of sleep. Such figures are consistent with previously re- 
ported 24-hour sleep amounts. For example, Aserinsky (1969) instructed 
subjects to "make e'^ery attempt to sleep" while confined to bed for 
30 hours (interrupted only twice for meals). During the first 24 hours 
(midnight to midnight) subjects obtained an average of 14.4 hours of 
sleep. During the 24-hGur period beginning at 7:30AM, after a full 



^>■=JA .^yc- 



o 



7 



night's sleep (mean =^ 7.04 hrs.), the inecin sleep duration v^as 12.98 hrs. 
This figure is in remarkable agreement with the average TST for each of 
the first 2 24--hour periods, subsequent to Night 2, in the present 
study (12.71 hrs.). In light of such findings, it appears that 12 to 
13 hours of sleep per 24 hours may be considered a close approximation 
of the maximum capacity for sleep (Aserinsky, 1969). However, at least 
three lines of evidence suggest that substantially shorter sleep times 
may represent the maximum point of sleep "need". First, it has been 
proposed that REM density may be a reflection of "satisfaction of a 
sleep need, or . . . the buildup of a pressure to awaken" (Aserinsky, 
1969, p. 155). It was found in that study that REM density reached 
maximum values after 7.5 to 10 hours of sleep. Secondly, under condi- 
tions of perceptual deprivation, subjects averaged about 12 hours of 
sleep during the first 24 hours, but subsequently reduced sleep lengths 
until they approached baseline levels (about 7.5 hrs.) by the third or 
fourth day of deprivation (Potter and Heron, 1972). Also in the present 
study, total sleep time during the second 24 hours of bedrest decreased 
almost 25% when compared with that of the first 24 hours. It might be 
speculated that the decline v/ould have continued, if bedrest had continued, 

Nevertheless, with the exception of the perceptual deprivation 
study cited above, all values of sleep satiation or fulfillment of 
sleep "need" substantialy exceed the 7- to 8~hour sleep durations 
typically reported for normal young adults. The interpretation of such 
findings may be generally separated into two opposing views. It has 
been suggested, on the one hand, that the extended sleep observed in 
unrestricted sleep regimens is a consequence of decreased sensory 
input (see for example, Nakagawa, 1980; Heron, 1957). Proponents of 



'■iR 



this view have speculated that an iinportant function of the sensory and 
perceptual systems is to maintain a waking level of arousal in the 
reticular activating system. In studies comparable to the present one, 
where conditions are maintained at a relatively constant level, and 
sensory stimulation is not only static but also depressed relative to 
normal levels, input from peripheral afferent pathways may be insuffi- 
cient to furnish the appropriate level of RAS activation, "In general, 
appropriate sensory stimulation is needed to maintain an arousal state 
in animal Ss but repetitive monotonous stimulation habituates the arousal 
reaction . . .," (Makaguawa, 1980, p. 532). In short the, according to 
this view, extended sleep is the result of neurological "boredom" and/or 
habituation. Implied in such a view is the notion that the extended 
sleep time observed under unrestricted or bedrest conditions is not 
representative of natural sleep tendency (or requirement), but rather, 
is simply one consequence of the organism's decreased requirement to 
process environmental stimuli and respond accordingly (Heron, 1957). 

This is analagous to Flanigan's (1971) suggestion that the extended 
sleep observed in nonhuman subjects maintained under controlled and 
highly favorable conditions (i.e., limited activity, plenty of food, no 
predators) may reflect the upper limits of sleep that are organismically 
possible, rather than that which is typical in the animal's natural 
habitats. 

In contrast, it has been suggested (see for example Webb and Agnew, 
1975a) that the extended sleep lengths characteristic of unrestricted 
sleep conditions are, in fact, "normal" and that typically reported 
sleep durations of 7 to 8 hours may actually be the product of chronic • 
sleep deprivation. In support of such a notion is the finding that 



39, 

only one third of a group of individuals who completed 6-nionth sleep 
diaries reported that they usually awakened spontaneously in the morn- 
ing. Further, half of the respondents in the study reported that they 
wore typically not well -rested upon awakening (Kleitman, Mull in. Cooper- 
man, and Titelbaum, 1937). The extension of sleep on weekends reported 
by most individuals also suggests a 'need' for more than the typically 
obtained weekday mean, Furtlier, it has been shown that after 3 consecu- 
tive nights of sleep,, restricted to a period between 11PM and 7AM (mean 
= 7.5 hrs), subjects slept an average of 2 hours longer on the 4th night 
when allowed to awaken spontaneously (Webb and Agnew, 1975a). The 
subjects in that study were not encouraged to extend sleep: indeed, they 
were "unaware that they would be allowed to sleep longer." 

Similarly; the subjects in the present study were given no in- 
structions relative to the maintenance of sleep and wakefulness during 
the bedrest period, yet they also obtained substantially more sleep than 
self-reported normal sleep durations. This seems to be suggestive of an 
inclination tov/ard, if not an actual 'need' for, more sleep than is 
typically obtained. Of interest is the observation that the extended 
sleep durations resulted not from a lengthening of sleep episodes 
initiated at night, but rather from the addition of day sleep periods. 
Nocturnal sleep (11PM to 7AM) per 24 hours did not exceed normal night 
sleep (7.8 h). However^ day sleep episodes contributed an average of 
approximately 5 hours to each 24-hour total. It might be speculated 
that the usual sacrifice of such day sleep periods is the source of our 
chronic sleep deprivation. On the other hand, the bedrest environment 
in the present study was highly monotonous, with novel sensory input 
severely curtailed. It is, therefore, likely that such conditions 



40 

contributed somewhat to the observed tendency for extended sleep times, 
as- v-.'ell . 

In trasleep Struc ture. The mean sleep stage proportions of the 
combined sleep periods during BP did not differ significantly from those 
of the baseline night (Night 2)^ and were within normal limits reported 
for young adult populations, although REM and slow wave sleep (SWS) were 
significantly reduced when compared to the normative sample used here. 
Such findings are in agreement with those reported by Webb and Agnew 
(1977) relative to the distribution of sleep stages in experimentally 
controlled, polyphasic sleep regimens. That is, despite influences from 
changes in sleep length, p'rior wakefulness and sleep onset times assoc- 
iated with various schedules of dispersed sleep, "when the total sleep 
obtained during these altered regimens is compared with baseline sleep 
on a 24-hour regimen, the basic structure of sleep persists" (p. 448). 
Also, in accord with previous reports of dispersed and nap sleep 
(Maron, Rechtschaffen and Wolpert, 1964; Moses, Hord, Lubin, Johnson, 
and Naitoh, 1975; Nakagawa, 1980; Webb and Agnew, 1977; Weitzman et al . , 
I 1974) the occurrence of REM sleep maintained a circadian pattern across 
the bedrest period. Sixty percent of total REM time occurred during 
sleep episodes initiated between llPM and 7AM. Further, while only 9 
of the 84 sleep periods recorded during BP contained no REM sleep, 8 of 
those sleep episodes occurred during the day, and 7 occurred between 2PM 
and 10PM. Finally, Figure 4 graphically points out the tendency of 
REM sleep to occur differentially at intervals across the 24-hour day, 
with maxima and minima of the circadian oscillation occurring between 
4 and 8AM and 4 and 8PM, respectively. Such data seem to underscore 
the tendency for REM sleep to occur differentially across the 24 hours. 



41 



The decrease in REM percent during the bedrest period, conipared 
to baseline, also appears to have been the consequence of the circadian 
placement of REM sleep. While total REM time was differentially 
obtained within a relatively circumscribed time block, total sleep 
time was influenced somewhat less by such contingencies. In addition, 
opportunities for day sleep, when REM was less likely to occur, occupied 
a larger percentage of the bedrest period than did night sleep time. As 
a result, over the bedrest period, absolute sleep time was augmented to 
a greater extent than was REM time, thereby lessening the proportion of 
TST spent in REM sleep. 

The decreased proportion of REM sleep recorded over the bedrest 
period may also be attributable, in part, to the decrease in mean sleep 
period length, relative to baseline, associated with BP. It has been 
shown that the amount of TST spent in REM sleep becomes pi^oportionately 
less with the reduction of sleep length (Webb and Agnew, 1977). Since 
mean sleep period length during the bedrest period was almost two-thirds 
less -than that for the baseline night (2,99 hrs. vs 8.75 hrs.), a corre- 
sponding decline in the proportion of REM sleep for the majority of sleep 
periods during BP would also be expected. 

The observed decrease in REM percent, however, may also be a 
reflection of the decreased mobility and/or lack of novel perceptual 
stimulation characteristic of the bedrest situation. Several investi- 
gations of sleep patterns during prolonged bedrest have repcrted similar 
declines in REM sleep (Aserinsky, 1969; Nakagawa, 1980; Ryback and Lewis, 
1971). In addition, Adey, Bors and Porter (1968) reported decreased 
porportions of REM sleep in quadraplegic patients, relative to normal 
amounts. The authors proposed that the diminished REM sleep was related 



42 

to "loss of most niotor perfonnance in the waking state," as well as the 
"absence of highly focused attention in complex motor activity." The 
finding by Ryback and Lewis (1971), that subjects who were permitted no 
exercise while confined to bed exhibited decreased REM sleep, while 
those who were allowed to exercise during bedrest did not exhibit such 
a decline, also provides some support for- this notion. In the present 
study, the finding that REMS percent decreased (albeit slightly) from 
the first to the second 24 hours, may likewise be interpreted as 
supporting an immobilization/sensory habituation effect on the amount 
of REM sleep obtained. 

A rather unexpected finding in the present study was that of an 
increase (though not significant) in the proportion of SWS, as the 
bedrest period progressed. In their examination of patients with high 
crevical lesions, Adey et al . (1968), reported the diminution of SWS 
as well as decreased REM percentage. As with REM sleep, the authors 
concluded that such a decline was the consequence of immobility. Thus, 
the findings of the present study appear contrary to what would be 
expected by an immobilization hypothesis. 

On the other hand, the results reported here are in accord with 
the findings relative to SWS reported by Ryback and Lewis (1971). 
The bedrest subjects in that study exhibited increases fn SWS with the 
nonexercise group showing the larger rise. These results were inter- 
preted by the authors as indicating that SWS may serve to "repair or 
maintain the muscular system" in response to the effects of atrophy, 
as well as hypertrophy. Thus, it would appear that a change in the 
proportion of SWS, in either direction, may be explained by one or the 
other version of an immobilization hypothesis. 



43 



However, it seerns somewhat unpai^simonious to have to employ both 
versions to satisfactorily explain the data in terms, of immobilization. 
In the present study, SWS comprised a smaller proportion of TST during 
BP than during the baseline night. The hypothesis proposed by Adey 
et aK is useful in explaining such results. Yet, within the bedrest 
period, there was an increase in the percentage of SWS from the first 
to the second 24 hours. These findings clearly require the Ryback and 
Lewis version. ■ 

Several observations seem to support an alternative explanation 
for the increase in SWS across the bedrest period, however. It has 
been shown (webb and Agnew- 1971, p. 1354) that "longer periods of 
wakefulness before sleep result in greater amounts of stage 4 sleep 
in the first 3 hours of sleep." In the present study, the mean inter- 
val between sleep episodes increased by some 70% (from 1.65 hrs. to 
2.82 hrs.) from the first to the second 24-hour period. At the same 
time, the proportion of SWS increased almost 25% (from 12.9% to 16%). 
By the same token, periods of wakefulness between sleep episodes 
averaged about 1 hour longer during the day than at night (3.32 hrs, vs 
2,29 hrs.). Correspondingly, SWS comprised a slightly greater propor- 
tion of day sleep than of night sleep episodes (16.2% vs 13.2%). The 
relationship between prior wakefulness and subsequent amounts of SWS 
seems apparent. 

Such an association would also account for the decline of SWS 
from Night 2 to the bedrest period. The amount of wakefulness proceed- 
ing the baseline night (14 to 17 hrs.) far exceeded the duration of 
waking intervals characteristic of BP. Consequently, the subsequent 
sleep periods reflected this difference by exhibiting differential 



44 

proportions of SWS sleep. Inconsistent with a prior wakefulness 
hypothesis, however, is the observation by several investigators that 
there is a SWS 'kick' in the records of extended sleep. That is, 
extended sleep is often characterized by the reappearance of substantial 
SWS episodes in the late morning. The possible significance of such a 
finding is considered later in the discussion. 

Results of the examination of the influence of prior sleep on the 
REM sleep cycle are best described as equivocal. Two examinations 
were made, one to test the notion that the REM cycle is sleep-dependent, 
the other to examine the possibility that the REM cycle is, instead, a 
sleep-independent rhythm bused on elapsed clock time, regardless of state. 
Support for both views may be found in the literature. For example. 
Globus (1956) found that the cycling of REM sleep demonstrated "at least 
in part" a tendency to be a time-locked, rather than a sleep-dependent, 
rhythm in the nap sleep of 2 subjects recorded for a total of 107 REM 
periods. This conclusion was based primarily on the observation that 
correlations between sleep onset and REM onset decreased at certain 
times in the afternoon (between noon and 3 PM). That is, during this 
interval sleep onset got progressively later while REM onset remained 
constant relative to real time. Yet, prior sleep was not considered 
and, therefore, the interpretation of such findings is problematic. 

In contrast, Moses et al . (1975) and Moses, Lubin, Johnson, and 
Naitoh (1977) reported findings which suggest that the REM sleep cycle 
is a sleep-dependent phenomenon. In the 1977 study, the nap sleep of 
25 subjects was 'compressed,' by subtracting all intervening waking 
periods, and then examined as a single sleep episode. The resulting 
mean REM cycle lengths did not differ significantly from those recorded 



45 

during base-line sleep. The same prccedure was carried out in the present 
study, and similar results were obtained. Using the- onset of the last 
REM period of Night 2 as a starting point, the mean REM cycle length was 
determined for subjects' 'compressed' bedrest periods, and compared to 
the mean cycle length for Night 2. The mean cycle length for the 
compressed period differed from the cycle length for Night 2 by less 
than 1 minute (96.84 min vs 96,56 min). Such evidence is strongly 
suggestive of a sleep-dependent cycle. 

In a second test^ each subject's mean REM cycle length for Night 2 
was superimposed on both his/her 'intact' bedrest period (i.e., includ- 
ing waking periods) and 'cc-mpressed' bedrest period. The mean deviation 
of an actual REM occurrence , from the onset of the hypothesized cycle , 
was used as a measure of 'goodness of fit.' The mean deviation across 
the 'compressed' bedrest period was 14.5 minutes. In other words, the 
actual occurrence of REM periods during BP differed by an average of 
about 15 minutes, as compared to expected occurrences, when intervening 
waking episodes were disregarded. Again, such a finding is supportive 
of a sleep- dependent REM sleep cycle. However, a similar finding that 
the mean deviation of actual REM sleep from hypothesized REM periods 
across the 'intact' bedrest period (15.8 min), precludes the acceptance 
of the sleep-dependence of REM sleep at the absolute exclusion of the 
'real time' model. 

Numerous studies of napping and dispersed sleep (Carskadon and 
Dement, 1975: Globus, 1966; Moses et al., 1975; Nakagawa, 1980; Webb 
et al , , 1956) have reported perturbations in the mode of appearance of 
REM sleep episodes, characterized by the onset of REM sleep within 
minutes of the initiation of a sleep period. The reported frequencies 



46 

of occurrence of such sleep onset REM periods (SOREMPS) have ranged 
from as few as 3 out of 107 REM episodes (Globus, 1966) to as many as 
21 of 34 REM episodes (Moses et al , , 1975). Maron et al . (1964) reported 
the occurrence of no REM onset periods in the examination of 18 subjects 
who napped in either the afternoon (about 1:30PM) or evening (about 
7:30PM). Yet, the overall rate of occurrence of SOREMPS for 5 studies 
of dispersed and nap sleep (Carskadon and Dement, 1975; Globus, 1966; 
Moses et al , , 1975: Nakagaua, 1980: Weitzman et al . , 1974) is rather 
substantial at 39% of all REM periods recorded (range 2.8% - 72%). 
Since such events are almost never observed in normal nocturnal sleep, 
SOREMPS have been considered to be indications of the overall disruption 
of normal sleep structure associated with day sleep episodes and 
dispersed sleep regimens (Weitzman et al . , 1974; Moses et al . , 1975), 

In the present study, of 153 REM episodes recorded over the bedrest 
period, only 3 were initiated at the beginning of a sleep period (i.e., 
before the appearance of 2 niin of stage 2). The infrequency of such 
occurrences suggests that the dispersed sleep of the present study may 
be of a different sort than typically observed nap sleep or experimen- 
tally dispoi^sed sleep. 

Such a view is further supported by the regularity with which sleep 
stages occurred across the bedrest period. Seventy percent of all- sleep 
periods recorded during BP were 'full blown' sleep episodes (61% of day 
sleep episodes); that is, all sleep stages were present. By comparison, 
only 16% of the 560 opportunities for sleep in the Weitzman et al . study 
contained all stages. Of the 80 naps examined by Moses et al . (1975), 
27.5% contained both SWS and REM sleep. REM sleep occurred in 90% of 
all sleep episodes during BP (86% of day sleep episodes), SWS occurred 



47 

in 85% of the sleep periods in this study {80% of day sleep periods). 
Again by comparison, the naps of subjects studied by Moses et al . 
contained REM episodes ^3% of the time; 35% of the sleep opportunities 
examined by Weitzm.an et al . contained REM and 48% contained SWS. 

Seven of the 9 sleep periods which contained no REM sleep occurred 
between 2PM and 10PM. Such a finding is consistent with previous ones 
that REM sleep typically increases in amount from midnight to morning 
and decreases toward evening (Moses et al . , 1975; Nakagawa, 1980; 
Weitzman et al . , 1974). It is likely, then, that the absense of REM 
during some sleep episodes in the present study were^ at least in part, 
due to circadian effects. 

A similar possibility also exists relative to 'missing' periods 
of SWS (specifically, stage 4). Several examinations of extended 
sleep (see for example, Gagnon and Dekoninck, 1981; Webb, Campbell and 
Hendlin, 1981) have noted the re-occurrence of stage 4 (in relatively 
large amounts) during the late morning. In the present study, sleep 
episodes characterized by the absence of stage 4 occurred across the 
entire day (6:40AM to 10:45 PM). It is interesting to note, however, 
that an obvious 'gap' occurred between 10:30AM and 2:20PM. That is, 
the sleep episodes initiated during those four hours always contained 
stage 4 sleep. Sleep periods initiated after about 11PM, and 
throughout the night, also contained stage 4. Thus, it might be 
suggested that the absence of stage 4 in 15% of the sleep episodes in 
this study, was the manifestation of the biphasic cycling of stage 4 
sleep, rather than a reflection of the disruption of normal sleep 
processes. A further indication of the possible bipolar nature of 
stage 4 is the observation that total stage 4 time for BP was evenly 
distributed between day and night (716 min vs 714 min). 



48 



Clearly, the differences in the appearance and sequencing of 
sleep stages between this study and the 2 studies of nap sleep with 
which it has just been compared, are attributable in large part to 
the difference in mean sleep episode length (3 hrs. vs 1 hr.) . This is 
especially true of REM sleep, if sleep dependency is assumed. Never- 
theless, the persistence and regularity with which sleep stages occurred 
across the bedrest period is noteworthy. There were no significant 
differences in the proportions of sleep stages between bedrest sleep 
and Night 2 sleep. Nor, were there significant changes in sleep stage 
percentages between the first and second 24 hours of bedrest. Final ly^ 
only REM sleep percent varied significantly relative to day or night 
onset times. 

Weitzman et al . (1974) noted that the sleep episodes which they 
observed were "clearly not mi natures of the normal 8 hr. sleep pat- 
tern." Such a view has been echoed by most others who have studied 
dispersed sleep and naps. Most of these studies have differed from 
the present one, in that the sleep periods were typically experi- 
mentally circumscribed^ rather than being placed on a 'self-demand' 
schedule. Such a methodological difference may account for the 
dissimilarity of results reported here. 

Yets Nakagawa (1980) also reported significant differences in 
day episodes versus baseline (night) sleep, despite the fact 
that the onset and termination of sleep periods was not regulated. 
Significant increases in stage 1, significant decreases in stages 4 
and REM and the presence of SOREMPS led Nakagawa to conclude that 
"daytime sleep itself might be characterized as a special sleep at 
the onset of the diurnal sleep-waking cycle," (p. 534). 



49 



In that study, Nakagawa noted a sleep/waking cycle of approxi- 
mately 4 hours, and suggested that a significant relationship seemed 
to exist betv.'een this cycle and the scheduling of meals. The quadri- 
phasic rhythm observed during the present study did not appear to be 
the result of feeding schedules, since less than half (42%) of waking 
periods were used for meals. Further, one subject (#932) fasted 
for the duration of the experiment, yet maintained the least variable 
sleep/waking cycle of the group. 

Uni phas ic or Ult radian? The results of the present study seem 
to suggest, then, that the daytime sleep observed was not a "special" 
sleeps but rather was the continuation of an ultradian sleep/waking 
rhythm, which nevertheless maintained a definite tendency to be 
weighted toward a nocturnal placement, relative to total sleep time. 

The regularity with which sleep episodes v;ere initiated across 
the bedrest period also seems to support the notion- of an ultradian 
pattern of sleep. The mean within-subject variability of the sleep/ 
waking cycles was 2.66 h (^--^SD). While the between-subject variability 
was similar (SD = 2.73), most of the variability was contributed by 
a single subject. This subject (#946, see Table II) exhibited a 
sleep/waking cycle (13.59 h) which more than doubled the mean sleep/ 
waking cycle length of the other 8 subjects (5.85 h). Likewise, the 
variability of the sleep/waking cycle of this subject (SD = 4.52) 
exceeded the group mean by almost twice (SD ^^ 2.43). Excluding this 
subject's sleep/waking cycle length from the group mean reduces the 
variability of the quadri phasic rhythm to less than an hour (SD = 
57 min). 



50 



.Such a pattern of variability is similar to that observed for 
the REM sleep cycle. The 90 to 100 minute REM cycle is of limited 
value in predicting the occurrence of REM episodes vnthin the sleep 
record of a single subject. Yet for a population, the predictability 
of a 90-100 minute cycle is quite good. 

A further indication of the regularity of the quadriphasic sleep/ 
v^aking cycle is the observation that the overall cycle length did 
not change significantly from one 24 hour period to the next. On 
the other hand^ the length of the sleep/waking cycle did differ as a 
function of day and nighty with the night cycle being substantially 
longer (7.8 hrs. vs 5.2 hrs.). It might be speculated that this 
difference was the consequence of subjects having spent the majority 
of their lives entrained to a monophasic sleep system, and that given 
time, the difference in cycle lengths might diminish. The present 
data do not support such a notion, however since the difference 
between night sleep/waking cycle length and day sleep/waking cycle 
length did not lessen significantly in the second 24 hours of bed- 
rest. 

The polyp!iasic distribution of the sleep of numerous animals 
under experimental conditions is well documented. Berger (1972) 
has noted that "if we wish to study comparative aspects of normal • 
sleep, we shouldn't impose wakefulness at any time on any species j 
including the human, but should take 24-hour recordings under equiva- 
lent conditions." The relatively basal activity levels, absence of 
novel perceptual stimulation and the satisfaction of bodily functions 
characteristic of the present experimental situation are comparable 



51 



to typical conditions under which animal sleep is studied. That a 
polyphasic sleep pattei^n was exhibited under such conditions, therefore, 
was not completely unexpected. Indeed, in 1972 Snyder speculated that 
"even in the human we would probably find polyphasic sleep if v^e used 
the same conditions that we use for animals." (p. 45). 

While the monotony of the situation was quite likely instrumental 
in the increase in total sleep time over the bedrest period, it seems 
less probable that such "neurological boredom" would be expressed in 
a cyclic manner. Yet, the possibility remains, as noted by VJeitzman 
(1972) with regard to the sleep cycle in cats. "In your experimental 
situation! .... you are measuring in part the shift ^f pattern which 
is taking place from a previous long-established light-dark pattern, in 
addition to adaptation to a strange new environment. Are you measuring 
the effect of that shift as well as the intrinsic rhythmicity in the 
cat? If the measured rhythmicity were constant over, say, several 
weeks, then it would support the concept that a basic rhythmicity was 
being measured. However, if it tended to change over 1, 2, or 3 weeks 
that would suggest that you are at least partially measuring an adapta- 
tion effect," (p. 201). Obviously, the question relative to human 
sleep cannot be VT^solved by results of the present experiment. 

It is suggested, though, that the conditions of the present study 
represented a further advancement along a continuum of slackened 
behavioral controls over the sleep process, the results of which was a 
clearer manifestation of an inherent ultradian sleep/waking rhythm, 
rather than the adaptation of the sleep response to a "strange new 
environment." It is further suggested that such a rhytlim, albeit in 



highly dampened fornix may also be reflected in the occasional naps 
taken by normal adults (especially on weekends) , the increased frequency 
of naps associated with the loosened schedules of geriatric and college 
populations, the sleep patterns of infants, and the polyphasic sleep 
patterning noted in unstructured environments (i.e., Arctic expeditions). 
And, I would suggest one additional manifestation of the ultradian 
nature of the sleep response. Webb (1969) has noted that "(no one yet 
has exploited a foundation to study the 'siesta' patterns of the tropi- 
cal and sui)tropical cultures, although at various odd moments, I am 
most tempted)/' (p, 58). Results of the present study may suggest 
that such a proposal, to examine cross-cultural diversity in the 
cycling of rest and activity, .may deserve a better fate than paren- 
thetical consideration. 



APPENDIX 1 
SLEEP QUESTIONNAIRE 



1. How many hours, on the average, do you usually sleep per night? 
less, 5, 5h. 6, 6h. 7, Ih, 8, &h, 9, 9^5, 10, more 

2, How many hours of sleep per night do you think that you need to 
feel well and function adequately? 

3.. How many hours of sleep per night do you prefer to have when you 
have a chance? 

4. In general 5 the amount of sleep that you usually get is: 

not enough about enough too much 

5. On the average , about how many naps do you usually take each week? 
0, 1, 2 J 3, 4, 5, 6, 7, 8, or more 

6. About how many total hours do you usually spend each week taking 
naps? 

7. About how many times on the average do you wake up each nigiit? 
0, 1, 2, 3, 4, 5, 6, 7, 8, or more 

8. About how much total time do you spend awake after going to sleep?, 
nonej, less than 5 min., 5-15, 16-30, 31-60, more 

9. About how many minutes does it typically take for you to go to 
sleep? less than 5, 5-15, 16-30, 31-60, more than 1 hour 



10. How often do you have trouble getting to sleep as quickly as you 
would like? Almost never, occasionally, often, almost always 

11. How much do you enjoy sleep? 

not at all, a little, moderately, much 

12. How regular are your bedtimes? 

very regular, somewhat regular, somewhat irregular, very 
irregular 

13. How regular are your wake-up times? 

very regular, somewhat regular, somewhat irregular, very 
irregular 

14. What is your average bedtime during weekdays? 



(to nearest 15 min.y 
53 



54 



15. What is your average bedtime on weekends? 

16. What is your average vrake up time on weekdays? 

17. What is your average wake up time on weekends? 



(to nearest 15 min. 



; 



fto nearest 15 min. ) 



(to nearest 15 min. 7 



18. How well do you usually sleep at night? 

Very well, satisfactorily, some problems, poorly. 

19. Do you usually feel well rested when you wake up, or soon thereafter 
Almost never, occasionally, often, almost always 

20. On the average, how many days per week do you usually go to bed 
more than one (1) hour earlier or later than your average bedtime? 
0, 1, 2, 3, t\, 5, 6, 7 

21. On the average, how many days per week do you usually wake up more 
than one (1) hour earlier or later than your usual v./ake up tirni?/ 
0, 1, 2, 3, 4, 5, 6, 7 ■ 

22. Do you consider your sleep ^or)] light or ^^^r)! deep? Check below, 
very light__ y^^v)! deep 

23. Do you feel tired during the day because you have slept poorly? 
Never sometimes often • always 

24. How much alcohol do you drink? 

.Never sometimes everyday 

25. Do you wake up before you intend to? 

, ^never 

once or twice a month 



_once or twice a week 
jiearly every day 



26. Do you use sleeping pills to get to sleep? 

^ ___n ever 

^about once a month 

^about once a week 

n early nightly 



27. What, if any, sleeping pills do you use? 

28. What, if any, prescription drugs are you presently taking? 



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55 



H*i.'Y'-,."F*T7>«c*,|"- • 



56 



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1958, 56(3), 271-274.^ 



57 



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58 



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BIOGRAPHICAL SKETCH 

Scott Searcy CamiDbeTI was born February 25, 1952. He received 
his B.A. degree, with a major in psychology, from Florida State 
University in 1974. From September, 1972, to dune, 1978, he attended 
Montana State University from which he received the M.S. degree in 
experim.ental psychology. In September, 1978, he continued his 
graduate studies, under the supervision of Wilse B. k'ebb, at the 
University of Florida. Upon completion of the Ph.D. degree, he 
accepted a postdoctoral fellowship at Harvard Medical School. 



60 



I certify that. I have read this study and that in my opinion 
it conforms to acceptable standards of scholarly presentation 
andisi'ully adequate, in scope and quality, as a dissertation for 
the deqree of Doctor of Philosophy. 






Li ric..A 



7\fl 



'y\. 



\f\j\^,. 



V 



Wilse B. Webbs Chairman 
Graduate Research Professor of 
Psychology 



I certify that I have read this study and that in my opini 
it conforms to acceptable standards of scholarly presentation 
and is fully adequate, in scope and quality, as a dissertation 
the deqree of Doctor of Philosophy. ■ <:z 



yO. 



on 
foi 




William K. Berg 
Professor of Psychology 



I certify that I have read this study and that in my opinion 
it conforms to acceptable standards of scholarly presentation 
and is fully adequate, in scope and quality, as a dissertation for 
the degree of Doctor of Philosophy 



Donald A. Dews bury ~ ~^ 
Professor of Psychology 



I certify that I have read this study and that in my opinion 
it conforms to acceptable standards of scholarly presentation 
and is fully adequate, in scope and quality^ as a dissertation for 
the degree -of Doctor of Philosophy. 




Charles M, Levy 
Professor of Psychology 



I certify that I have read this study and that in my opinion 
it conforms to acceptable standards of scholarly presentation and 
is fully adequate s in scope and quality, as a dissertation for the 
degree of Doctor of Philosophy. 



J' 



/ 



-f 



")0^..A-£thi^Jl 



■Jack R. Siiiitli 
Professor of Electrical 
Engineering 



This dissertation vvos submitted to the Graduate Faculty of the 
Department of Psychology in the College of Liberal Arts and 
Sciences and to the Graduate Council, and was accepted as partial 
fulfillment of the requirements for the degree of Doctor of 
Philosophy. 



August 1979 



Dean for Graduate Studies and 
Research